Correct answer is the second option: "The letter was <em>sent</em> by a disgruntled customer."
The first option refers to the decimal unit.
The third option refers to arranging for the transport of something.
The last option refers to a smell.
The sentence that is correctly punctuated with commas, semi-colons or periods is sentences number 2: "the crab grass was flourishing, but the rest of the lawn, unfortunately, was dying."
The fist option is incorrect because there are no breaks at all in the sentence. The third asnwer is incorrect as well because there should have been a comma for a pause after mentioning that the grass was flourishing, but then adding a different element to the sentence such as the word "unfortunately", which indicates that something not expected happened to the grass. And finally the last asnwer is incorrect because the semi-colon is used in the wrong way.
Commas indicate small breaks, while periods indicate the end of a sentence. Semi-colons are used to separate different elements from the same idea in a sentence.
There are a few rules to using commas. One of those rules is not separating a subject from its verb. For example:
- "My mom, is a great dancer". INCORRECT
- "My mom is a great dancer". CORRECT
Another rule is that in a compound predicate that contains two verbs, you can't separate them with a comma. For example:
- "Agatha sings, and dances". INCORRECT
- "Agatha sings and dances". CORRECT.
